// Copyright (c) Six Labors.
// Licensed under the Six Labors Split License.

using System.Numerics;
using System.Runtime.CompilerServices;
using BenchmarkDotNet.Attributes;

namespace SixLabors.ImageSharp.Benchmarks.General.PixelConversion;

public class PixelConversion_ConvertToVector4_AsPartOfCompositeOperation
{
    private struct ConversionRunner<T>
        where T : struct, ITestPixel<T>
    {
        private T[] source;

        private Vector4[] dest;

        public ConversionRunner(int count)
        {
            this.source = new T[count];
            this.dest = new Vector4[count];
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public void RunRetvalConversion()
        {
            int count = this.source.Length;

            ref T sourceBaseRef = ref this.source[0];
            ref Vector4 destBaseRef = ref this.dest[0];

            Vector4 temp;

            for (nuint i = 0; i < (uint)count; i++)
            {
                temp = Unsafe.Add(ref sourceBaseRef, i).ToVector4();

                // manipulate pixel before saving to dest buffer:
                temp.W = 0;

                Unsafe.Add(ref destBaseRef, i) = temp;
            }
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public void RunCopyToConversion()
        {
            int count = this.source.Length;

            ref T sourceBaseRef = ref this.source[0];
            ref Vector4 destBaseRef = ref this.dest[0];

            Vector4 temp = default;

            for (nuint i = 0; i < (uint)count; i++)
            {
                Unsafe.Add(ref sourceBaseRef, i).CopyToVector4(ref temp);

                // manipulate pixel before saving to dest buffer:
                temp.W = 0;

                Unsafe.Add(ref destBaseRef, i) = temp;
            }
        }
    }

    private ConversionRunner<TestRgba> runner;

    [Params(32)]
    public int Count { get; set; }

    [GlobalSetup]
    public void Setup()
    {
        this.runner = new ConversionRunner<TestRgba>(this.Count);
    }

    [Benchmark(Baseline = true)]
    public void UseRetval()
    {
        this.runner.RunRetvalConversion();
    }

    [Benchmark]
    public void UseCopyTo()
    {
        this.runner.RunCopyToConversion();
    }

    // RESULTS:
    //     Method | Count |     Mean |    Error |   StdDev | Scaled | ScaledSD |
    // ---------- |------ |---------:|---------:|---------:|-------:|---------:|
    //  UseRetval |    32 | 120.2 ns | 1.560 ns | 1.383 ns |   1.00 |     0.00 |
    //  UseCopyTo |    32 | 121.7 ns | 2.439 ns | 2.281 ns |   1.01 |     0.02 |
}
